• Journal of Korean Society of Water and Wastewater
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• v.17 no.4
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• pp.495-502
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• 2003

In order to modify incorrect flow data in the sewage system, the method using the stage-discharge relation and hydraulic characteristic curve of sewer pipe are applied. The modified data were verified with field measured data and the infiltration analysis using the modified data was carried out. When flowrate were measured using the flow-meter in fair weather, the stage data were comparatively consistent but velocity data were very poor for the most part. Therefore, it was recommended that sewage flowrate variation characteristic curve and infiltration were computed using the modified data on the basis of stage data. Especially, in the case of using the hydraulic characteristic curve, extrapolation results of the rainy season flowrate using regression curve on the basis of the data in fair weather were also reasonable.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1347-1352
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• 2001

In this study, the acoustic properties of polyester sound absorbing materials with three different bulk densities were investigated by calculating and measuring the acoustic parameters in terms of characteristic impedance, propagation constant, and absorption coefficient. For the calculations, Delany and Bazley's empirical equation was used together with the experimentally obtained specific flow resistivities under steady flow conditions. For the experimental measurements, the well-known two-thickness method was accessed. The experimentally measured values of characteristic impedance and propagation constant were generally agreed well with the corresponding calculated values. Based on the comparisons between the calculations and measurements, it was found that the magnitude of the absorption coefficient was closely related to the characteristic impedance and the real part of the propagation constant. Especially, the maximum magnitude of the absorption coefficient was depended upon the imaginary part of the propagation constant indicating the phase change of the propagation constant.

• International Journal of Fluid Machinery and Systems
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• v.6 no.1
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• pp.18-24
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• 2013

In order to apply the design method of diagonal flow fan based on axial flow design to the design of radial-outflow type diagonal flow fan which has lower specific speed of 600-700 [$min^{-1}$, $m^3/min$, m], radial-outflow type diagonal flow fan which specific speed was 670 [$min^{-1}$, $m^3/min$, m] was designed by a quasi three-dimensional design method. Experimental investigations were conducted by fan characteristics test, flow surveys by a five-hole probe and a hot wire probe. Fan characteristics test agreed well with the design values. In the flow survey at rotor outlet, the characteristic region was observed. Two flow phenomena are considered as the cause of the characteristic region, one is tip leakage vortex near rotor tip and another is pressure surface separation on the rotor blade.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.16-21
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• 2016

This study is a numerical analysis of the flow characteristic of a quick coupler. The quick coupler is a popular coupling tool for pipelines in hydraulic and pneumatic systems. In this study, the flow characteristic of a quick coupler outlet is conducted about the flow coefficient. The quick coupler is analyzed for improving flow and confirmed with the study results. The velocities with pressure distribution according to inlet and outlet pressure drop of the coupler are also compared. The flow coefficient is analyzed according to the flow analysis result for each pressure drop. When the pressure drop is 1 psi, the flow coefficient (Cv) matched about 98% of the value provided by the actual product.

• The KSFM Journal of Fluid Machinery
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• v.11 no.1
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• pp.9-17
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• 2008

A numerical study for three-dimensional laminar flow in the entrance region of helical tubes connected with straight ones is carried out to investigate the effects of Reynolds number, pitch and curvature ratio on the oscillation periods of the flow. The fully elliptic governing equations were solved by means of a finite volume method. The fully developed laminar flow boundary condition was applied at the straight tube inlet. This results cover a curvature ratio range of 1/10${\sim}$1/320, a pitch range of 0.0${\sim}$3.2, and a Reynolds number range of 62.5${\sim}$2000. A comparison is made with previous experimental correlations and numerical data. The developments of velocity, local and average friction factors are discussed. The average friction factors are oscillatory in the entrance region of helical pipes. It has been found that the angle required for the flow to be similarly developed is most affected by the curvature ratio. The pitch and Reynolds number do not have any significant effect on the angle. The characteristic angle ${\phi}_c(={\phi}/sqrt{\delta})$, or the characteristic length to diameter ratio $s_c(=l\sqrt{\delta} cos(atan{\lambda})/d)$, can be useful to represent the development of flow in helical tubes. As the pitch increases and as the curvature ratio and Reynolds number decrease, the amplitude and the number of flow oscillations along the main streamwise direction decrease.

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.35-44
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• 2006

Operation conditions of a reheat cycle gas turbine for a combined cycle power plant was analyzed. Based on measured performance parameters of the gas turbine, a performance analysis program predicted component characteristic parameters such as compressor air flow, compressor efficiency, efficiencies of both the high and low pressure turbines, and coolant flows. The predicted air flow and its variation with the inlet guide vane setting were sufficiently accurate. The compressor running characteristic in terms of the relations between air flow, pressure ratio and efficiency was presented. The variations of the efficiencies of both the high and low pressure turbines were also presented. Almost constant flow functions of both turbines were predicted. The current methodology and obtained data can be utilized for performance diagnosis.

• Journal of Biomedical Engineering Research
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• v.33 no.4
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• pp.177-183
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• 2012

The inspiratory flow rate of a human is changed with the amount of the workload. The flow characteristic is affected by the inspiratory flow rate. In the flow field of airway, the both of turbulence intensity and secondary flow affect the deposition pattern of particles which is important for the drug-aerosol targeting. Thus the analysis of the flow characteristic in a human airway is important. The purpose of this study is to investigate the effects of the inspiratory flow rate on the flow characteristics in a human airway. The tubular airway is consistent with the oral cavity, pharynx, larynx and trachea. The relatively inspiratory flow rate is used at each case of human states regarding the workload. By the effect of geometric airway changes, transition to turbulent airflow after the larynx can occur with relaminarization further downstream. The low Reynolds number k-${\omega}$ turbulence model is used for analysis with flow regime. As the inspiratory flow rate is larger, the turbulence kinetic energy and secondary flow intensity increase in airway. On the other hand, the area of recirculation zone is smaller.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.75-83
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• 2001

In this paper, numerical analysis is used to find the effects of inclination of rear end on flow characteristic around an automobile. The reference slant angle of rear end is 28.6$^{\circ}$, the slant angle of rear end is decreased to 24$^{\circ}$, 26.6$^{\circ}$ and also increased to 31.6$^{\circ}$, 36.4$^{\circ}$. The 3-D incompressible Navier-Stockes equations are solved by the iterative time marching scheme. The computed surface pressure coefficients were compared with experimental results and a good agreement has been achieved. The A- and C-pillar vortex and other flow phenomena around the ground vehicle are evidently shown. The variation of aerodynamic coefficients of drag, lift with respect to inclination angle of rear end are systematically studied. The flow characteristic on the automobile surface with respect to change of inclination of rear end have been also studied.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.4
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• pp.76-90
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• 2018

Despite the growing use of SNS and the increasing number of recruitment related to SNS, little research has been conducted between career preparation activities and relationship with SNS. Therefore, this study investigates the relationships among purpose of using instagram, flow of instagram and career preparation behavior using structural equation model, and by investigating the adjustment effect of the personal characteristic among them. To this end an online survey was conducted for students who want to be cabin crew. The results of this study show that motivation of using instagram had a positive and significant effect on flow of instagram, which in turn positively influenced career preparation behavior. Furthermore, it could be confirmed that there was a adjustment moderating effect on personal characteristic between purpose of using instagram and flow of using instagram. The results of this study suggest that the likelihood of recruitment for being cabin crew can be achieved by identifying mutual relationships among motivation of using instagram, flow of instagram, career preparation behavior, and personal characteristics.

• Wind and Structures
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• v.22 no.5
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• pp.555-571
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• 2016

A hanging-type sand-retaining wall is a very common sand-blocking fence structure used to prevent sand movement. This type of wall is widely used along the Qinghai-Tibet and Gobi desert railways in Xinjiang, Western China. To analyze the characteristics of wind-sand flow fields under the effect of such a sand fence structure, a wind tunnel test and a field test were carried out. The wind tunnel test showed the zoning characteristics of the flow fields under the effect of the hanging-type sand-retaining wall, and the field test provided the sediment transport data for effective wind-proof interval and the sand resistance data in the front and behind the sand-retaining wall. The consistency of the wind-sand flow fields with the spatial distribution characteristic of wind-carried sand motion was verified by the correspondences of the acceleration zone in the flow field and the negative elevation points of the percentage variations of the sand collection rate. The spatial distribution characteristic of the field sand collection data further showed the spatial structural characteristic of the sandy air currents under the action of the hanging-type sand-retaining wall and the sand resistance characteristic of the sand-retaining wall. This systematic study on the wind-sand flow fields under the control of the hanging-type sand-retaining wall provides a theoretical basis for the rational layout of sand control engineering systems and the efficient utilization of a hanging-type sand-retaining wall.